This invention relates to, and has among its objectives, biocidal treatment of water bodies so that stable response of an oxidation-reduction potential sensor is provided.
Commonly-owned application Ser. No. 09/323,348, filed Jun. 1, 1999, now U.S. Pat. No. 6,303,038 B1, issued Oct. 16, 2001, describes solid mixtures of dialkylhydantoins and bromide ion sources for water sanitation. Commonly-owned copending application Ser. No. 09/484,844, filed Jan. 18, 2000, describes chemical processes from which compositions of the present invention can be formed or derived. Commonly-owned application Ser. No. 09/484,687, filed Jan. 18, 2000, now U.S. Pat. No. 6,508,954 B1, issued Jan. 21, 2003, describes 1,3-dibromo-5,5-dimethylhydantoin particulate solids producible by the processes of Application Ser. No. 09/484,844, such solids having unprecedented enhanced properties, and compacted articles made from such particulate solids without use of a binder. Commonly-owned application Ser. No. 09/483,896, filed Jan. 18, 2000, now U.S. Pat. No. 6,448,410 B1, issued Sep. 10, 2002, relates to the granulation of small average particle size 1,3-dibromo-5,5-dimethylhydantoin and also to the compaction of such granulated products to form larger-sized articles. Commonly-owned application Ser. No. 09/484,891, filed Jan. 18, 2000, now U.S. Pat. No. 6,495,698 B1, issued Jan. 17, 2003, relates to the compacting of 1,3-dihalo-5,5-dimethylhydantoins other than 1,3-dibromo-5,5-dimethylhydantoin without use of binders, and to the novel compacted forms so produced. Commonly-owned application Ser. No. 09/484,938, filed Jan. 18, 2000, now U.S. Pat. No. 6,565,868 B1, issued May 20, 2003, describes using 1,3-dibromo-5,5-dimethylhydantoin for microbiological or biofilm control in water. Commonly-owned copending application Ser. No. 09/487,816, filed Jan. 18, 2000, relates in part to converting 1,3-dihalo-5,5-dimethylhydantoins into compacted articles using novel binders. Commonly-owned copending application Ser. No. 09/775,516, filed Feb. 2, 2001, describes microbiological control in aqueous media achieved by introducing a microbiocidally effective quantity of one or more 1,3-dibromo-5,5-dialkylhydantoins into the aqueous medium. Commonly-owned copending application Ser. No. 09/778,228, filed Feb. 2, 2001, describes biocidally-active 1,3-dibromo-5,5-dialkylhydantoin biocidal compositions in readily identifiable forms. Commonly-owned copending application Ser. No. 09/893,581, filed Jun. 28, 2001, describes microbiological control in poultry processing using a halogen-based microbiocide or 1,3-dihalo-5,5-alkylhydantoin.
It is the goal of any owner or operator of recreational water bodies, swimming pools, spas, hot tubs or the like to provide pool water which is maintained so that there are no detrimental microorganisms. To this end, the pool owner or operator may choose from a wide variety of biocidal chemical systems to ensure that a biocidally effective amount of water-treating agents is present in the water body on a continuous basis.
The more commonly used biocidal agents are halogen-containing biocides. As referred to herein, halogen or halo- refers to either chlorine or bromine. These agents register as xe2x80x9cfree chlorinexe2x80x9d or xe2x80x9cavailable chlorinexe2x80x9d species in commonly used testing procedures. Persons using biocidal agents in the biocidal treatment of water customarily, if not universally, refer to xe2x80x9cfree chlorinexe2x80x9d level as a measure of biocidal control, even though the agent may contain bromine as the oxidizing species. The EPA has determined that a level of 1.0-1.5 ppm of available chlorine should be maintained at all times to continuously kill the microorganisms and algae in such water systems. The active bromine level may be expressed as free chlorine for ease of comparison to industry standards. For example, the biocide, 1,3-dibromo-5,5-dimethylhydantoin, hydrolyzes into 2 molecules of HOBr, which registers as xe2x80x9cfree chlorinexe2x80x9d species in commonly-used standard test procedures for determining the quantity of halogen-containing microbiocidal agent to be used for water treatment. To convert such chlorine values to active bromine values, the chlorine value should be multiplied by 2.25. Thus, in bromine-containing systems sanitation is maintained when the active bromine, as Br2, is 2.0 to 3.0 ppmw.
Among the available techniques for indicating the concentration of biocidal agent present in the water system, two are used most often. In the more preferred system, an electronic Oxidation-Reduction Potential (ORP) sensor, linked to a controller device, is a sophisticated and labor efficient tool for indicating a level of halogen present which is consistent with satisfactory sanitation quality. Therefore, many commercial pool operators and some private pool owners possess ORP (Oxidation-Reduction Potential) monitoring probes interfaced to a controller. The controller electronically actuates a valve to control a flow of water to a chemical feeding device or activates a delivery pump for delivery of a biocidal chemical to the water system. When a sensing electrode of either platinum or gold, comes in contact with a solution containing species for which the probe is sensitive, an electrical potential develops at the electrode""s surface. The magnitude of the potential relates to the concentration of the species being measured, so that the higher the potential, the higher the species concentration. In a recreational pool situation, the species present which presents a variation in concentration causing a change in potential is the active species of the biocidal chemical, such as active bromine. The ORP reading may be equated to the concentration of the active bromine and reported as a xe2x80x9cfree chlorinexe2x80x9d value as per the industry naming convention. The ORP probe is pre-set to a particular mV range and will signal the controller when the mV condition deviates outside this range necessitating addition of the appropriate biocidal chemical. When sufficient amount of biocidal chemical has been delivered to the water such that the pre-set ORP condition is attained, the controller de-activates the switch to the feeding device so that no more biocidal chemical is released into the water.
The use of an ORP sensor allows the pool operator to measure the potential generated by the active form of the biocidal chemical. Additionally, ORP monitoring has an advantage in that it is an ongoing electronic process requiring no test chemicals or agents after initial stabilization. Monitoring of sanitation levels is constantly performed as opposed to being performed on some predetermined schedule basis.
Another method of water management and treatment is use of the DPD test kit which utilizes a chemical reaction between a water sample, N,Nxe2x80x2-diethyldiphenylenediamine (DPD) and a buffer to cause a color change which can be visibly compared to a color chart of halogen concentrations. The use of a DPD test kit by a pool operator or pool technician requires the operator to sample the water, add appropriate reagent(s) and visually compare the color change of the pool water sample against a color standard chart to arrive at an approximation of the active chlorine or bromine value. If the operator employs the DPD test as the sole monitoring method, the operator, after testing, must take steps to add an appropriate biocidally effective amount of the treatment agent to the water. Thus this method tends to require more time and effort than the ORP method.
Typically, the operator will employ the DPD test kit procedure as a check on the ORP sensor reading during the initial stabilization time interval of the ORP sensor reading in a water facility which has been drained and re-filled or in which the biocidal agent is being changed.
When the pool ORP monitoring system is initially started up, either with untreated water or with water in which the biocidal agent of choice is to be changed, e.g. from a chlorine-containing system to a bromine-containing system, the pool operator may observe a phenomenon known as xe2x80x9cORP bouncexe2x80x9d for as long as several weeks. ORP bounce describes a condition where, for the same active bromine residual quantity in the water, different (usually lowered) ORP responses are detected. This situation seems to be transient, and the water system eventually becomes stabilized. Having a system which exhibits a long stabilization time for the ORP reading creates a labor intensive situation for the pool operator. The operator must frequently check the ORP reading against a manually determined DPD test kit halogen value to ensure correct treatment by the automatic controller system.
When a body of water has been initially treated with N,Nxe2x80x2-dihalo-5,5-dialkylhydantoin, it has been observed that, though the independent DPD test yields a steady value of bromine, the ORP mV reading is inconsistent. Because the ORP sensed value is vital to the proper functioning of the controller, the operator must frequently re-adjust the ORP reading when it falls to prevent a false ORP reading from triggering the addition of too much biocidal agent by the controller.
It would be advantageous if a method could be found that would significantly shorten the stabilization time period of a newly started up recreational body of water so that ORP values would quickly and reliably indicate satisfactory active bromine levels.
This invention provides an efficient and effective way of reducing the stabilization time of a newly started up recreational body of water.
This invention involves, inter alia, the discovery that, where biocidal treatment with N,N-dihalo-5,5-dialkylhydantoin is being initialized in a recreational water body, baseloading the water with some bromide ion and dialkylhydantoin stabilizes the ORP response in a matter of hours rather than over several weeks. Thus, a method of overcoming the highly undesirable and lengthy xe2x80x9cORP bouncexe2x80x9d condition has been found where, heretofore, no solution for this problem existed.
An embodiment of the invention is a process for stabilizing the oxidation-reduction potential of a recreational body of water before initially treating the water with one or more N,N-dihalo-5,5-dialkylhydantoins. The process comprises baseloading the water with bromide ion and dialkylhydantoin and thereafter treating the water with at least one N,N-dihalo-5,5-dialkylhydantoin. Use of this process can substantially shorten the time required for the ORP sensor reading to stabilize.
Another embodiment of this invention is a method of reducing the interval of time of stabilizing the oxidation-reduction potential of a recreational body of water which has not been treated with an N,Nxe2x80x2-dihalo-5,5-dialkylhydantoin biocidal agent or which does not contain residues resulting from prior addition thereto of an N,Nxe2x80x2-dihalo-5,5-dialkylhydantoin biocidal agent, which method comprises conducting the following steps:
A) introducing into said body of water at least one water-soluble source of bromide ion and at least one dialkylhydantoin, in which the alkyl groups each contain independently in the range of 1 to about 4 carbon atoms; then
B) introducing into said body of water at least one N,Nxe2x80x2-dihalo-5,5-dialkylhydantoin in which one halogen atom is a bromine atom and the other halogen atom is either a bromine atom or a chlorine atom, and in which one alkyl group is a methyl group and the other alkyl group contains in the range of 1 to about 4 carbon atoms; and
C) determining when the oxidation-reduction potential of said body of water has become stabilized.
Use of the methods of this invention results in substantial reduction in the period of time required for the treated body of water such as a swimming pool, spa, or the like, to achieve a stable oxidation-reduction potential. Concurrently the methods of this invention shorten the period of time required for the treated water to reach the point at which one can be assured that the active bromine content of the treated water is at a suitable biocidal concentration, as determined by means of an ORP controller equipped with an ORP sensor probe. Consequently, rather than having to wait for a period of, say, three weeks before such ORP stability has been achieved, persons can make use of the stabilized, treated body of water much sooner. Moreover, the pool operator has the assurance that the body of water being used contains the requisite biocidal concentration of active bromine as indicated by the ORP controller readings.
A further embodiment of this invention is a recreational body of water is described to which has been added in sequence, bromide ion, dialkylhydantoin, and N,N-dihalo-5,5-dialkylhydantoin. The body of water, after the additions, has a stable ORP sensor reading.
The alkyl groups of the dialkylhydantoin each contain independently in the range of 1 to about 4 carbon atoms. In the N,N-dihalo-5,5-dialkylhydantoin, one halogen atom is a bromine atom and the other halogen atom is a bromine atom or a chlorine atom, and one alkyl group is a methyl group and the other alkyl group contains in the range of 1 to about 4 carbon atoms.
Other embodiments, features, and advantages of this invention will be still further apparent from the ensuing description and appended claims.